Abstract
Banding is one of the image artifacts for
electrophotographic (EP) printers. Due to its origin within
the EP process, it can also be viewed as an intrinsic
signature of the specific printer. Modulating the EP process
to generate banding signals that are below the human visual
threshold but can be detected by effective detection
approach can further extend the signature capacity. This
deliberate banding signal can be viewed as extrinsic
signature of a printer. Since modulating the printing process
provides significant barrier of entry, it is effective in
limiting the attack possibilities and can be an effective
method to embed needed information regarding the
document and the device it was printed on to provide
unprecedented forensic information. One of the key issues
with embedding extrinsic signature is the information
should not be detectable by the human observer. However,
the signature needs to be detectable by a suitable detection
algorithm. In this paper, we will propose one method to
modulate the exposure of the EP process to embed
controlled quasi-periodic signature into a document. Based
on the system level modeling and experimental verification
of the EP process, machine detectable signatures that are
below the human visual threshold can be embedded into a
printed document without any perceivable degradation in
image quality. Preliminary experiment results confirm our
hypothesis that with properly designed control techniques,
effective extrinsic signatures can be embedded into a
document.
